Typical communication networks may transmit information in one or more signal formats, such as an optical carrier level-n (OC-n) format, an synchronous transport signal level-n format (STS-n), a digital service level-n (DS-n) format, frame relay format or combination of these or other signal formats. In addition these various signal formats may contain, for example, time-division multiplexed information, asynchronous transfer mode cells, or other types of information formats. As communication systems evolve and interface with various network elements, issues arise in handling various signal formats requiring various levels of signal processing.
One approach to addressing these issues is to incorporate separate switching complexes at nodes within the network, each switching complex operable to process a particular signal type or a particular granularity of signal. For example, a network node may include one switching complex operable to process traffic carrying time division multiplexed information, and a separate switching complex operable to process traffic carrying asynchronous transfer mode cells. This approach is expensive, difficult to manage, and generally requires an inordinate amount of space.
Another approach is to carry time-division multiplexed information over asynchronous transfer mode traffic. This approach is typically accomplished using asynchronous transfer mode circuit emulation techniques. A problem with this approach is that mapping time-division multiplexed information onto asynchronous transfer mode traffic generally introduces error-causing jitter into the system. In addition, since the time-division multiplexed information is mapped into an asynchronous format, this approach eviscerates synchronous optical network (SONET) ring protection, which would otherwise be available.